Environmental Risk and Risk of Resistance Selection Due to Antimicrobials' Occurrence in Two Polish Wastewater Treatment Plants and Receiving Surface Water.

In this study, a screening of 26 selected antimicrobials using liquid chromatography coupled to a tandem mass spectrometry method in two Polish wastewater treatment plants and their receiving surface waters was provided. The highest average concentrations of metronidazole (7400 ng/L), ciprofloxacin (4300 ng/L), vancomycin (3200 ng/L), and sulfamethoxazole (3000 ng/L) were observed in influent of WWTP2. Ciprofloxacin and sulfamethoxazole were the most dominant antimicrobials in influent and effluent of both WWTPs. In the sludge samples the highest mean concentrations were found for ciprofloxacin (up to 28 µg/g) and norfloxacin (up to 5.3 µg/g). The removal efficiency of tested antimicrobials was found to be more than 50% for both WWTPs. However, the presence of antimicrobials influenced their concentrations in the receiving waters. The highest antimicrobial resistance risk was estimated in influent of WWTPs for azithromycin, ciprofloxacin, clarithromycin, metronidazole, and trimethoprim and in the sludge samples for the following antimicrobials: azithromycin, ciprofloxacin, clarithromycin, norfloxacin, trimethoprim, ofloxacin, and tetracycline. The high environmental risk for exposure to azithromycin, clarithromycin, and sulfamethoxazole to both cyanobacteria and eukaryotic species in effluents and/or receiving water was noted. Following the obtained results, we suggest extending the watch list of the Water Framework Directive for Union-wide monitoring with sulfamethoxazole.

Distribution and ecological risk of pharmaceuticals in surface water of the Yeongsan river, Republic of Korea.

This study examined the distribution of pharmaceuticals in Yeongsan River and at point sources (PSs) in the associated water system, and performed a risk assessment based on our findings. The samples included effluents collected from three sewage treatment plants (PS1, PS2, and PS3) and two industrial complexes (PS4 and PS5) as well as surface water collected from seven mainstreams and 11 tributaries of the river. The target pharmaceuticals were acetylsalicylic acid, carbamazepine, clarithromycin, naproxen, sulfamethazine, sulfamethoxazole, sulfathiazole, and trimethoprim, which were detected by liquid chromatography-tandem mass spectrometry. All pharmaceuticals except acetylsalicylic acid and sulfathiazole were found in PS1, PS2, and PS3 samples, whereas acetylsalicylic acid, carbamazepine, sulfamethazine, and sulfamethoxazole were found in PS4, most of the pharmaceuticals were not present in PS5. The rank order of pharmaceutical concentration in surface water was carbamazepine (97.2%, 0.2067 µg/L) > sulfamethoxazole (88.9%, 0.1132 µg/L) > naproxen (51.4%, 0.0516 µg/L) > clarithromycin (43.1%, 0.0427 µg/L). The distribution of pharmaceuticals in the Yeongsan River at PSs and non-PSs differed, and higher concentrations of human pharmaceuticals were detected in upstream and midstream areas whereas higher concentrations of animal pharmaceuticals were found downstream. Hazard quotients (HQs) evaluated at each sites based on mean concentration and 95% upper confidence limits (95% UCLs) were all less than one, indicating a low risk of toxicity. The findings of this study are expected to be useful for risk assessment of aquatic ecosystems.

Capillary electrophoresis with capacitively coupled contactless conductivity detection method development and validation for the determination of azithromycin, clarithromycin, and clindamycin.

A capillary electrophoresis with capacitively coupled contactless conductivity detection based method for the assay of azithromycin, clarithromycin and clindamycin was optimized and validated in this study. A buffer solution of 20 mM 2-(N-morpholino) ethane sulfonic acid, 40 mM l-histidine and 0.6 mM cetyltrimethylammonium bromide (pH 6.39) was used for the electrophoresis. An uncoated, bare-fused silica capillary (total length 60 cm, effective length 32 cm, 75 µm id) was used at 25°C. The sample was injected hydrodynamically at 0.5 psi for 5 s. The electrophoresis was conducted at 30 kV in reverse polarity for 6 min with 3 and 2 min of in-between sodium hydroxide (0.1 M) and background electrolyte rinsing, respectively. Ammonium acetate was used as internal standard. This simple and robust method showed reasonable limit of detection and limit of quantitation for azithromycin (0.0125/0.03 mg/mL), clarithromycin (0.017/0.03 mg/mL), and clindamycin (0.038/0.06 mg/mL), with good selectivity, precision both intraday (relative standard deviation ≤ 1.0%) and interday (relative standard deviation < 3.7%), linearity (R2  > 0.999) and recovery (99 - 101.7%). The method was successfully applied for the determination of azithromycin, clarithromycin and clindamycin in formulations.

Group determination of 14-membered macrolide antibiotics and azithromycin using antibodies against common epitopes.

Erythromycin (ERY), clarithromycin (CLA), roxithromycin (ROX), and azithromycin (AZI) are macrolide antibiotics widely used in livestock and human medicine. Therefore, they are frequently found as pollutants in environmental water. A method based on indirect competitive enzyme-linked immunosorbent assay (ELISA) for group determination of these macrolides in foodstuffs, human biofluids, and water was developed. Carboxymethyloxime of clarithromycin (CMO-CLA) was synthesized and conjugated to bovine serum albumin (BSA) and gelatin to prepare immunogen and coating antigen with advantageous presentation of target epitopes, l-cladinose and d-desosamine, common for these analytes. Antibodies generated in rabbits were capable of recognizing ERY, CLA, and ROX as a group (100-150%), and AZI (12%) and did not cross-react with ERY degradants, which lack antibiotic activity. Assay displayed sensitivity of determination of 14-membered macrolides (IC50=0.13-0.2ng/ml) and low limit of detection (LOD) that was achieved at 0.02 to 0.03ng/ml. It allowed performing analysis of milk, muscle, eggs, bovine serum, water, human serum and urine, and avoiding matrix effect without special pretreatment using simple dilution with assay buffer. For 15-membered macrolide AZI, the corresponding characteristics were IC50=1.6ng/ml and LOD=0.14ng/ml. The recoveries of veterinary and human medicine macrolides from corresponding matrices were validated and found to be satisfactory.

Analysis of Distribution of Ingredients in Commercially Available Clarithromycin Tablets Using Near-Infrared Chemical Imaging with Principal Component Analysis and Partial Least Squares.

The aim of this study was to evaluate pharmaceuticals using a near-infrared chemical imaging (NIR-CI) technique for visualizing the distribution of ingredients in solid dosage forms of commercially available clarithromycin tablets. The cross section of a tablet was measured using the NIR-CI system for evaluating the distribution of ingredients in the tablet. The chemical images were generated by performing multivariate analysis methods: principal component analysis (PCA) and partial least squares (PLS) with normalized near-infrared (NIR) spectral data. We gained spectral and distributional information related to clarithromycin, cornstarch, and magnesium stearate by using PCA analysis. On the basis of this information, the distribution images of these ingredients were generated using PLS analysis. The results of PCA analysis enabled us to analyze individual components by using PLS even if sufficient information on the products was not available. However, some ingredients such as binder could not be detected using NIR-CI, because their particle sizes were smaller than the pixel size (approximately 25×25×50 µm) and they were present in low concentrations. The combined analysis using both PCA and PLS with NIR-CI was useful to analyze the distribution of ingredients in a commercially available pharmaceutical even when sufficient information on the product is not available.

[Occurrence Characteristics and Ecological Risk Assessment of Antibiotics in Reclaimed Water-receiving Rivers in Beijing].

Taking Liangshui River, the reclaimed water-receiving river in Beijing, as the research area, the types, detection frequencies, and concentrations of 16 antibiotics in water and sediment were analyzed, and their temporal-spatial variation and occurrence characteristics were discussed. The results showed that nine and 13 target antibiotics were detected in the water and sediment of Liangshui River, with the antibiotic concentration ranges of ND-116.68 ng·L-1 and ND-235.42 ng·g-1, respectively. The main antibiotics in water were ofloxacin and clarithromycin, and the main antibiotic in sediment was ofloxacin. The total concentration of antibiotics in water and sediment showed a gradual decrease from the upstream to the downstream in the Liangshui River mainstream, and the concentration of antibiotics in tributaries was higher than that in the mainstream. The inflow of tributaries had an obvious impact on the antibiotic concentration in water for the Liangshui River but had little impact on its sediment. The total concentration of antibiotics in water and sediment during the dry season was generally higher than that during the wet season. The detected antibiotics with the highest concentration were quinolones in water during the wet season and macrolides in the dry season. Quinolones had the highest concentration in sediment in both seasons. The ecological risk assessment results showed that clarithromycin had a low risk in water in the dry season and sediment in both seasons, whereas the other antibiotics had no risk. The combined ecological risk and the most sensitive trophic level ecological risk assessment showed that all sampling sites had low risk or no risk, and the risk of the dry season was generally greater than that of the wet season. The risk values of some sampling points were close to the medium risk threshold during the dry season, which requires further attention.

Minimum Inhibitory Concentrations before and after Antibacterial Treatment in Patients with Mycobacterium abscessus Pulmonary Disease.

The clinical importance of Mycobacterium abscessus (MABS) pulmonary disease has been increasing. However, there is still a lack of information about MIC distribution patterns and changes in clinical practice settings. The MIC results of rapidly growing mycobacteria isolated from 92 patients with nontuberculous mycobacterial pulmonary disease diagnosed from May 2019 to March 2021 were retrospectively analyzed. Most of the patients (86 patients; 93.5%) were infected with MABS; 46 with Mycobacterium abscessus subsp. abscessus (Mab), and 40 with Mycobacterium abscessus subsp. massiliense (Mma). Significant differences in susceptibility to clarithromycin (15.2% versus 80.0%, P < 0.001) and azithromycin (8.7% versus 62.5%, P < 0.001) were observed between Mab and Mma. Most isolates were susceptible to amikacin (80; 93.0%), and over half were susceptible to linezolid (48; 55.8%). Only one-quarter of isolates (22, 25.6%) were susceptible to imipenem, while more than half (56; 65.1%) had intermediate susceptibility. Fifty-one isolates (59.3%) had MIC values of less than 1 µg/mL for sitafloxacin, which were significantly higher than isolates for moxifloxacin (5; 5.8%), especially in Mab. Sixty-five (75.6%) isolates had MICs of less than 0.5 µg/mL to clofazimine. Two patients showed obvious MIC result changes: from susceptible to resistant to clarithromycin and from resistant to susceptible to amikacin and imipenem. In conclusion, MABS isolates were relatively susceptible to amikacin and linezolid, and clarithromycin and azithromycin were especially effective against Mma. In addition, sitafloxacin and clofazimine had low MICs and might be effective treatment agents. IMPORTANCE The MICs of isolates from 86 patients with Mycobacterium abscessus (MABS); 46 with Mycobacterium abscessus subsp. abscessus (Mab), and 40 with Mycobacterium abscessus subsp. massiliense (Mma) were retrospectively analyzed. The main findings are as follows: (i) Mma were significantly more susceptible to clarithromycin and azithromycin than Mab, and both subspecies tended to be more susceptible to clarithromycin than azithromycin. (ii) Most isolates were susceptible to amikacin (93.0%), and over half to linezolid (55.8%). (iii) Fifty-one isolates (59.3%) had MIC values of less than 1 µg/mL for sitafloxacin, and 65 (75.6%) had less than 0.5 µg/mL for clofazimine, which seems worth clinical investigating. (iv) Among nine cases analyzed chronological changes, only two patients showed obvious MIC result changes even after the long-term multidrug treatment. The present study revealed MICs of MABS clinical isolates before and after treatment in clinical settings, which could help develop future MABS treatments strategies.

Chitosan-genipin microspheres for the controlled release of drugs: clarithromycin, tramadol and heparin.

The aim of this study was to first evaluate whether the chitosan hydrochloride-genipin crosslinking reaction is influenced by factors such as time, and polymer/genipin concentration, and second, to develop crosslinked drug loaded microspheres to improve the control over drug release. Once the crosslinking process was characterized as a function of the factors mentioned above, drug loaded hydrochloride chitosan microspheres with different degrees of crosslinking were obtained. Microspheres were characterized in terms of size, morphology, drug content, surface charge and capacity to control in vitro drug release. Clarithromycin, tramadol hydrochloride, and low molecular weight heparin (LMWH) were used as model drugs. The obtained particles were spherical, positively charged, with a diameter of 1-10 microm. X-Ray diffraction showed that there was an interaction of genipin and each drug with chitosan in the microspheres. In relation to the release profiles, a higher degree of crosslinking led to more control of drug release in the case of clarithromycin and tramadol. For these drugs, optimal release profiles were obtained for microspheres crosslinked with 1 mM genipin at 50 °C for 5 h and with 5 mM genipin at 50 °C for 5 h, respectively. In LMWH microspheres, the best release profile corresponded to 0.5 mM genipin, 50 °C, 5 h. In conclusion, genipin showed to be eligible as a chemical-crosslinking agent delaying the outflow of drugs from the microspheres. However, more studies in vitro and in vivo must be carried out to determine adequate crosslinking conditions for different drugs.

Development of a latex particles-based lateral flow immunoassay for group determination of macrolide antibiotics in breast milk.

A lateral flow immunoassay (LFIA) using latex particles labeled with antibody to BSA-clarithromycin (CLA) was developed for the rapid simultaneous group determination of six macrolide antibiotics. Optimization of antigen spotting on the membrane and latex probe loading allowed improving visual detectability (vLOD) 100 times, which was 1, 1, 10, 10, 50, and 1000 ng/mL for CLA, roxithromycin, erythromycin, dirithromycin, azithromycin, and oleandomycin in buffer, respectively. The calculated limits of instrumental detection (cLOD) were respectively 0.12, 0.15, 1.4, 2.1, 2.4, and 3.3 ng/mL. To avoid a strong influence of breast milk of a very diverse and variable composition, a sample pretreatment is proposed. The six macrolides mentioned can be visually detected in breast milk after 20 min pretreatment at concentrations of 10-1000 ng/mL or instrumentally with cLOD of 4.0, 2.5, 30, 42, 42 and 180 ng/mL. The recovery rate from the spiked samples carried out using a strip scanner device ranged from 71 % to 110 %, and precision expressed as relative standard deviation was between 3-14 %. The described rapid on-site diagnostic assay format can be useful for monitoring the content of antibiotics in breast milk during macrolide treatment to ensure safe breastfeeding of infants.

Prioritised pharmaceuticals in German estuaries and coastal waters: Occurrence and environmental risk assessment.

In this study a target analysis approach with method detection limits down to 0.01 ng L-1 was developed in order to determine ultra-trace pharmaceuticals in seawater of the German coast and their estuaries. The selection of target analytes based on a prioritisation commissioned by the German Environmental Agency considering occurrence in German surface waters, production volumes and ecotoxicological data. Using ultra-high pressure liquid chromatography coupled to a triple quadrupole mass spectrometer equipped with an electrospray ionisation source 21 prioritised pharmaceuticals out of seven therapeutical classes (antibiotics, iodinated X-ray contrast media (ICM), analgesics, lipid reducers, antiepileptics, anticonvulsants, beta-blockers) have been detected in the low to medium ng L-1-range. The most frequently measured substance groups in the German Baltic Sea and German Bight are the ICM, represented by the non-ionic ICM iomeprol (German Bightmax: 207 ng L-1; Baltic Seamax: 34.5 ng L-1) and the ionic ICM amidotrizoic acid (German Bight: 86.9 ng L-1), respectively. The same pattern of substance distribution could be detected in the German Bight, the German Baltic Sea and their inflows with lower concentrations in the offshore region that are partly a result of dilution with marine water. Pharmaceuticals entering the estuaries and coastal regions are an environmental issue since data on the ecotoxicological effects on aquatic marine organisms is limited. Especially the antibiotics clarithromycin and sulfamethoxazole could be ecotoxicologically/environmentally critical.

Quantitative analysis of in vitro compatibility of binary and ternary mixtures of nitroimidazole and macrolides in combination with omeprazole using a calorimetric technique.

In the present study, in vitro interactions between nitroimidazoles, macrolides and omeprazole in binary and ternary mixtures were examined by measuring their enthalpy of solution (delta(sol)H) using a calorimetric technique. A comparison of the enthalpy of solution of the pure drugs with those of binary and ternary mixtures at pH 2 and 6 was made to indicate the magnitude of interaction between them. The delta(sol)H for all the nitroimidazoles is endothermic at pH 2 and 6 but both the macrolides show exothermic behavior, whereas the enthalpy of solution of omeprazole changes from -40.52 to 4.35 kJmol(-1) as the pH changes from 2 to 6. The results have been quantified by determining the excess enthalpy of solution for both binary and ternary systems. The small deviations from ideality for all the binary systems are attributed to various non-bonding interactions between different functional groups on both the drug molecules. The results suggest compatibility of drug pairs in their binary mixtures. However, ternary mixtures show somewhat larger interactions. The magnitude of interaction enthalpy of a ternary mixture comprising tinidazole, clarithromycin and omeprazoles which are available as a marketed kitshas been calculated to be significant, suggesting that the three drugs cannot be co-formulated.

Liquid Chromatographic-Chemometric Techniques for the Simultaneous HPLC Determination of Lansoprazole, Amoxicillin and Clarithromycin in Commercial Preparation.

Two multivariate calibration-prediction techniques, principal component regression (PCR) and partial least-squares regression (PLSR) were applied to the chromatographic multicomponent analysis of the drug containing lansoprazole (LAN), clarithromycin (CLA) and amoxicillin (AMO). Optimum chromatographic separation of LAN, CLA and AMO with atorvastatin as the internal standard (IS) was obtained by using Xterra® RP18 column 5 µm 4.6 × 250 mm2, and 25 mM ammonium chloride buffer prepared ammonium chloride, acetonitrile and bidistilled water (45:45:10 v/v) as the mobile phase at flow rate 1.0 mL/min. The high pressure liquid chromatography data sets consisting of the ratios of analyte peak areas to the IS peak area were obtained by using diode array detector detection at five wavelengths (205, 210, 215, 220 and 225 nm). LC-chemometric calibration for LAN, CLA and AMO were separately constructed by using the relationship between the peak-area ratio and training sets for each analyte. A series of synthetic solutions containing different concentrations of LAN, CLA and AMO were used to check the prediction ability of the PCR and PLS. Both of the two-chemometric methods in this study can be satisfactorily used for the quantitative analysis and for dissolutions tests of multicomponent commercial drug.

Selecting optimal columns for clarithromycin impurity analysis according to the quantitative relationship of hydrophobic subtraction model.

Hydrophobic subtraction model (HSM) is widely applied to select columns of equivalent or different selectivity compared with a reference column, but its application in identifying optimal columns for specific separations of real samples is rare. In this work, a column selection method was proposed by firstly directly correlating separation selectivity of different pairs of solutes to column parameters based on the quantitative relationship of HSM and then selecting the optimal columns according to the predicted selectivity in consideration of the total separation of all critical pairs of solutes. Three critical pairs of solutes in clarithromycin impurity analysis were evaluated as examples. Starting with the analysis of clarithromycin impurities on 15 columns with different selectivities, ten optimal columns were finally identified for clarithromycin impurity analysis from the HSM column characterization database containing nearly 600 columns and two of them were validated with satisfactory separations for all critical peak pairs. The proposed methodology was also compared to the traditional column selection procedure based on calculations of scalar measures of the Euclidean distance between chromatographic columns. Results showed that our method provides an effective way to find the desired columns that may be overlooked by the traditional column selection due to selection of an inappropriate reference column or overestimation of column similarity, such as Fs introduced in HSM.

Degradation of macrolide antibiotics by ozone: a mechanistic case study with clarithromycin.

Macrolide antibiotics are widely used (in the order of 1g per person per year). They pass the body largely unchanged and are also not degraded in wastewater treatment plants. With not too much effort, they may be eliminated from their effluents by ozonation. The macrolide antibiotics have all a dimethylamino group at one of the carbohydrate residues in common. This functional group is the target of the ozone reaction, and clarithromycin has been selected here for a more detailed study. Since only the free amine reacts with ozone, the rate of reaction is pH dependent (at pH 7: k = 4 x 10(4) M(-1) s(-1)). In analogy to the ozonolysis of trimethylamine, the main reaction is a transfer of an O-atom yielding the N-oxide (identified by HPLC/MS-MS). A minor product (10%, based on formaldehyde yields) is demethylated clarithromycin (identified by HPLC/MS-MS). The dimethylamino group is thought to be essential for the binding of the macrolide antibiotics to their target. As a consequence, chemical changes of this functional group, notably the formation of the N-oxide that is no longer a proton acceptor, inactivates these drugs as assayed by the suppression of the growth of Pseudomonas putida. This is most important for wastewater treatment, as mineralization of clarithromycin by ozone would require 100 times as much ozone.

A validated spectrofluorometric assay for the determination of certain macrolide antibiotics in pharmaceutical formulations and spiked biological fluids.

This paper describes a simple spectrofluorometric method for the analysis of 4 macrolide antibiotics. The method is based on the condensation of 10% (w/v) malonic acid and acetic acid anhydride under the catalytic effect of tertiary amine groups of the studied macrolides. The relative fluorescence intensity of the condensation product was measured at 397/452 nm (excitation/emission) for azithromycin dihydrate and at 392/445 nm (for clarithromycin, erythromycin ethylsuccinate, and roxithromycin. All variables affecting the reaction conditions were studied. The effects of potential interference due to common excipients, such as starch, lactose, sucrose, glucose, gum acacia, and magnesium stearate, as well as trimethoprim and sulfisoxazole acetyl formulated in primomycin capsules and pediazole oral suspension, respectively, were studied. A validation study for the proposed method was carried out according to U.S. Pharmacopeia 2002. The linearity ranges were 3-80 ng/mL for all of the cited macrolides. The limit of detection range was 0.74-1.20 ng/mL, while the limit of quantitation range was 2.47-4.02 ng/mL. The method was applied for the assay of the studied macrolides in pure pharmaceutical formulations and in spiked biological fluids. Results were compared with those obtained from the reported method, where calculated t- and F-values indicated high accuracy and good precision for the proposed method.

Occurrence of levofloxacin, clarithromycin and azithromycin in wastewater treatment plant in Japan.

Residual pharmaceutical products in sewage and other water environments have recently become a serious social problem in advanced countries. Among these pharmaceutical products, antibiotics have attracted special attention due to their serious impact on the ecosystem and connections to the emergence of drug-resistant bacteria. Our research intended to develop a new method to analyse the three antibiotics estimated to be released out of the body in large amounts in Japan; levofloxacin (LVFX), clarithromycin (CAM) and azithromycin (AZM), and survey the state of pollution in the sewerage. The concentrations of the water-phase antibiotics LVFX, CAM and AZM were measured in each process of activated sludge process in six wastewater treatment plants. Liquid chromatography tandem mass spectrometry (LC/MS/MS) was used to analyse solutions of the antibiotics after pretreatment with a solid phase extraction. The limits of quantification and the average recoveries for these antibiotics in the influent were 1.2 to 29 ng/L and 46 to 93%, respectively. In the influent, LVFX, CAM and AZM were detected at concentrations of 552, 647 and 260 ng/L, respectively, while their removal efficiencies were 42, 43 and 49%, respectively. Although the CAM and AZM concentrations decreased as the treatment progressed, it was shown that the LVFX concentration increased in activated sludge reactors in some cases. Despite differences in octanol-water partition coefficients among LVFX, CAM and AZM, their removal efficiency showed no major difference. This indicates that this removal phenomenon cannot be explained by simple adsorption by the activated sludge.

Reduced persistence of the macrolide antibiotics erythromycin, clarithromycin and azithromycin in agricultural soil following several years of exposure in the field.

The macrolide antibiotics erythromycin, clarithromycin and azithromycin are very important in human and animal medicine, and can be entrained onto agricultural ground through application of sewage sludge or manures. In the present study, a series of replicated field plots were left untreated or received up to five annual spring applications of a mixture of three drugs to achieve a nominal concentration for each of 10 or 0.1mgkg(-1) soil; the latter an environmentally relevant concentration. Soil samples were incubated in the laboratory, and supplemented with antibiotics to establish the dissipation kinetics of erythromycin and clarithromycin using radioisotope methods, and azithromycin using HPLC-MS/MS. All three drugs were dissipated significantly more rapidly in soils with a history of field exposure to 10mgkg(-1) macrolides, and erythromycin and clarithromycin were also degraded more rapidly in field soil exposed to 0.1mgkg(-1) macrolides. Rapid mineralization of (14)C-labelled erythromycin and clarithromycin are consistent with biodegradation. Analysis of field soils revealed no carryover of parent compound from year to year. Azithromycin transformation products were detected consistent with removal of the desosamine and cladinose moieties. Overall, these results have revealed that following several years of exposure to macrolide antibiotics these are amenable to accelerated degradation. The potential accelerated degradation of these drugs in soils amended with manure and sewage sludge should be investigated as this phenomenon would attenuate environmental exposure and selection pressure for clinically relevant resistance.

Modulation of microenvironmental pH and utilization of alkalizers in crystalline solid dispersion for enhanced solubility and stability of clarithromicin.

Clarithromycin (CAM) is known to be poorly water-soluble and acid-labile drug. Various alkalizers such as MgO, Na2CO3, Na2HPO4 and NaHCO3 were utilized to modulate the microenvironmental pH (pHM) and to improve the low stability and solubility of CAM in a crystalline-solid dispersion system (CSD). Polyvinylpyrrolidone (PVP K-30) and hydroxypropylmethylcellulose (HPMC) 4000-based CSDs containing alkalizers were prepared by cosolvent precipitation followed by evaporation process. The dried-CSDs mixed with microcrystalline cellulose, 2% croscarmellose sodium, and 1% magnesium stearate was then directly compressed into tablet. A dissolution test was carried out in 900 mL of pH 5.0 buffer solutions at 37 °C with a 50 rpm paddle speed. pHM, surface morphology, and structural behaviors were investigated. The dissolution rates of CAM in CSD containing alkalizers were improved. The drug in CSD remained crystalline as observed by differential scanning calorimetry and powder X-ray diffraction. Scanning electron microscopy revealed nearly identical images regardless of the sorts and amounts of carriers. PVP-based CSD tablet without alkalizer showed greater drug release, while HPMC-based CSD tablet without alkalizer retarded drug release due to its greater swelling capability. However, when the alkalizers were added in CSD tablet, the drug release was sharply increased. NaHCO3 induced the most rapid drug release while MgO retarded drug dissolution. Alkalizers in CSD also could maintain the pHM of the tablet above pH 5 under acidic conditions. The use of pH modifiers in CSDs could provide a useful method to improve the dissolution rate and stability of CAM via modulation of pHM without changing drug crystallinity.

Suppressed Release of Clarithromycin from Tablets by Crystalline Phase Transition of Metastable Polymorph Form I.

The pharmaceutical properties of clarithromycin (CAM) tablets containing the metastable form I of crystalline CAM were investigated. Although the dissolution rate of form I was higher than that of stable form II, the release of CAM from form I tablet was delayed. Disintegration test and liquid penetration test showed that the disintegration of the tablet delayed because of the slow penetration of an external solution into form I tablet. Investigation by scanning electron microscopy revealed that the surface of form I tablet was covered with fine needle-shaped crystals following an exposure to the external solution. These crystals were identified as form IV crystals by powder X-ray diffraction. The phenomenon that CAM releases from tablet was inhibited by fine crystals spontaneously formed on the tablet surface could be applied to the design of sustained-release formulation systems with high CAM contents by minimizing the amount of functional excipients.

Penetration of clarithromycin into middle ear fluid of children with acute otitis media.

OBJECTIVE: To determine the steady state plasma and middle ear fluid concentrations of clarithromycin and its metabolite, 14(R)-hydroxyclarithromycin in 32 pediatric patients with acute otitis media. METHODS: After the sixth dose of a 7.5-mg/kg every-12-h regimen of clarithromycin suspension, tympanocentesis was performed at 2, 4, 8 or 12 hours postdose. Plasma and middle ear fluid samples were assayed for concentrations of clarithromycin and its 14-hydroxy metabolite. RESULTS: Mean middle ear fluid concentrations ranged from 3.0 to 8.3 micrograms/g during the dosing interval for clarithromycin and from 1.5 to 3.8 micrograms/g for 14(R)-hydroxyclarithromycin. The mean middle ear fluid concentrations were consistently greater than corresponding mean plasma concentrations, which ranged from 0.7 to 3.4 micrograms/ml for clarithromycin and from 0.8 to 1.8 micrograms/ml for 14(R)-hydroxyclarithromycin. The ratios of middle ear fluid to plasma concentration appeared to increase during the dosing interval and were 8.8 and 3.8 for clarithromycin and 14(R)-hydroxyclarithromycin, respectively, 12 h after dosing. CONCLUSIONS: Multiple oral doses of clarithromycin suspension produced sustained middle ear fluid concentrations of clarithromycin and 14(R)-hydroxyclarithromycin which exceed the minimum inhibitory concentrations of most otic pathogens.